Method of operating a wind park

ABSTRACT

Wind power installations were initially always erected in the form of individual units and it is only in recent years that, caused also by administrative and building regulations, wind power installations are frequently installed in wind parks. In that respect a wind park in its smallest unit is an arrangement of at least two wind power installations, but frequently markedly more. By way of example mention may be made of the wind park at Holtriem (East Frisia) where more than 50 wind power installations are set up in an array. It is to be expected that the number of units and also the installed power of the wind power installations will also increase greatly in the forthcoming years. In most cases the wind potential is at its greatest in regions of the power supply networks with a low level of short-circuit power and low population density. It is precisely there that the technical connection limits are quickly reached by the wind power installations, with the result that it is then no longer possible for further wind power installations to be set up at such sites. A method of operating a wind park comprising a plurality of wind power installations, wherein the wind park is connected to an electrical power supply network into which the electrical power produced by the wind park is fed and the wind park and/or at least one of the wind power installations of the wind park has a control input, by means of which the electrical power of the wind park or one or more individual wind power installation or installations can be set in a range of between 0 and 100% of the respective power to be made available, in particular the nominal power, and that there is provided a data processing apparatus which is connected to the control input and by means of which the setting value is set in the range of between 0 and 100%, depending on how great is the power that the overall wind park provides at its output for feeding into the energy network and wherein the operator (PSU) of the electrical supply network to which the wind park is connected can adjust the power delivered by the wind park by way of the control input.

The invention concerns a method of operating a wind park and also a windpark as such.

Wind power installations were initially always erected in the form ofindividual units and it is only in recent years that, caused also byadministrative and building regulations, wind power installations arefrequently installed in wind parks. In that respect a wind park in itssmallest unit is an arrangement of at least two wind powerinstallations, but frequently markedly more. By way of example mentionmay be made of the wind park at Holtriem (East Frisia) where more than50 wind power installations are set up in an array. It is to be expectedthat the number of units and also the installed power of the wind powerinstallations will also increase greatly in the forthcoming years. Inmost cases the wind potential is at its greatest in regions of the powersupply networks with a low level of short-circuit power and lowpopulation density. It is precisely there that the technical connectionlimits are quickly reached by the wind power installations, with theresult that it is then no longer possible for further wind powerinstallations to be set up at such sites.

A conventional wind park which is connected by way of example to a 50 MWtransformer substation can therefore have at a maximum only 50 MW totalpower, that is to say for example 50 wind power installations each with1 MW nominal power.

Bearing in mind that wind power installations are not constantlyoperated in the nominal mode and thus the overall wind park also doesnot constantly reach its maximum power (nominal power), it can be foundthat the wind park is not put to optimum use if the nominal power of thewind park corresponds to the maximum possible total power which can befed in.

The invention accordingly proposes a solution in which the wind park hasa total power output which is higher than the maximum possible networkfeed-in power. When applied to the above-indicated example the power canbe raised to a value of over 50 MW, for example 53 MW. As soon as thewind speeds are sufficiently high to produce the limit power of 50 MWthe wind park regulating system according to the invention comes intoplay and regulates individual or all installations down when the overallmaximum power output is exceeded in such a way that it is alwaysobserved. This means that, at wind speeds above the nominal wind (windspeed at which a wind power installation reaches its nominal power), atleast one or all installations are operated with a (slightly) throttledpower output (for example at a power level of 940 kW instead of 1 MW).

The advantages of the invention are apparent. Overall the networkcomponents of the feed network (network components are for example thetransformer and the lines) can be put to optimum use or can have theirloads balanced in the optimum fashion (utilisation thereof up to thethermal limit is also a possibility). In that way existing wind parkareas can be better utilised, by virtue of setting up a maximum possiblenumber of wind power installations. The number is then no longer (soseverely) limited by the existing network capacity.

For controlling/regulating a wind power installation it is desirable ifit has a data input, by means of/by way of the electrical power can beset in a range of between 0 and 100% (with respect to the nominalpower). If for example a reference value of 350 kW is applied to thatdata input, then the maximum power output of that wind powerinstallation will not exceed the reference value of 350 kW. Any valuefrom 0 to the nominal power (for example from 0 to 1 MW) is possible asa reference value.

That data input can be used directly for power limitation purposes.

It is however also possible by means of a regulator to regulate thegenerator power output in dependence on the network voltage (in the windpark network or in the feed-in network).

A further important function will be discussed hereinafter on the basisof wind park regulation. It will be assumed for example that a wind parkcomprises 10 wind power installations which each have a nominal poweroutput of 600 kW. By virtue of the capacitances of the networkcomponents (line capacitances) or the limited capacitances in thetransformer substation it will further be assumed that the maximum powerto be delivered (limit power) is limited to 5200 kW.

There is now the possibility of limiting all wind power installations toa maximum power of 520 kW by means of the reference value (data input).That provides that the requirement for limiting the power to bedelivered is always met.

Another possibility involves not allowing the maximum power as the sumof all installations to be exceeded, but at the same time producing amaximum amount of energy (kW-hours (work)).

In that respect it should be recognised that, at low to moderate windspeeds within the wind park, it frequently happens that the wind powerinstallations at the advantageous (good) sites (these are the siteswhich the wind first encounters within the wind park) receive a greatdeal of wind. If now all wind power installations are simultaneouslycontrolled down to their throttled value (for example all to 520 kW),that produced power is admittedly attained by some wind powerinstallations arranged at good sites, while some other wind powerinstallations which however are in the ‘wind shadow’ of the well-locatedwind power installations (in the second and third rows) have less windand as a result operate for example only at 460 kW power and do notreach the value of the maximum throttled power of 520 kW. The overallpower output from the wind park is accordingly therefore substantiallybelow the allowed limit power output of 5200 kW.

The wind park power regulation according to the invention in that caseregulates the individual installations in such a way that the maximumpossible energy yield is set. This means in specific terms that forexample the installations in the first row (that is to say at goodsites) are regulated to a higher power (for example to the nominal power(therefore no throttling action). Therefore the overall electrical powerin the wind park rises. Park regulation however regulates eachindividual installation in such a way that the maximum allowedelectrical connection power is not exceeded while at the same time thework produced (kWh) reaches a maximum value.

Wind park management in accordance with the invention can be easilyadapted to the respective situations which arise. Thus for example it isvery simple to effect different throttling in respect of the power ofindividual installations if an individual one or a plurality ofinstallations of a wind park are (or have to be) taken from the network,if for maintenance reasons or other reasons an individual installationor a plurality of installations have to be temporarily stopped.

For controlling/regulating the wind park or the individual installationsit is possible to use a data/control processing apparatus which isconnected to the data inputs of the installations and which, from thewind speed data which are ascertained (by each installation), ascertainsthe respective most advantageous power throttling value for anindividual installation or for the entire wind park.

FIG. 1 is a block circuit diagram showing the control of a wind powerinstallation by means of a microprocessor μP connected to an inverterapparatus (PWR), by means of which multi-phase alternating current canbe fed into the power supply network. The microprocessor has a powerinput P, an input for inputting a power factor (cos phi) and an inputfor inputting the power gradient (dP/dt).

The inverter apparatus comprising a rectifier, a rectifier intermediatecircuit and an inverter is connected to the generator of a wind powerinstallation and receives therefrom the energy produced by thegenerator, in rotary speed-variable fashion, that is to say, independence on the rotary speed of the rotor of the wind powerinstallation.

The design illustrated in the Figure serves to illustrate how the powerdelivered by a wind power installation can be limited in its amount to amaximum possible network feed-in value.

FIG. 2 is a view showing the principle of a wind park comprising forexample three wind power installations 1, 2 and 3 of which—as viewedfrom the direction of the wind—two are disposed in side-by-siderelationship and the third is positioned behind the first two. As eachof the individual wind power installations has a power input for settingthe power of the respective installation (FIG. 1), the power levels ofan individual wind power installation can be set to a desired value bymeans of a data processing apparatus, by means of which the entire windpark is controlled. In FIG. 2 the advantageous sites for the wind powerinstallations are those which the wind first encounters, that is to saythe installations 1 and 2.

The present invention also concerns a method of operating a wind parkhaving at least one wind power installation with an electrical generatordrivable by a rotor for delivering electrical power to an electricalnetwork to which the wind power installation is connected. The inventionfurther concerns a wind power installation comprising a rotor and anelectrical generator coupled to the rotor for delivering electricalpower to an electrical consumer, in particular an electrical network.

In the case of low-power electrical (island) networks the networkfrequency rises very quickly (abruptly) if a relatively large consumeris separated from the electrical network. The drive machines such as forexample diesel engines, water wheels and the like require some time inorder then to reduce their (mechanical and electrical) power. Duringthat period of time those generators produce more energy than is takenfrom the electrical network. That energy is then consumed foraccelerating the generators. That means that the rotary speed and thusalso the network frequency rises.

As many electrical devices, for example computers, electric motors andthe like, which are connected to the electrical network, are however notdesigned for fluctuating network frequencies or abrupt changes therein,that can result in damage to electrical machines, even going as far asdestruction thereof.

The object of the present invention is to eliminate the above-describedproblems when wind power installations (a wind park) are connected tothe electrical network.

According to the invention that object is attained by a method havingthe features set forth in claim 7 and a wind power installation havingthe feature set forth in claim 10. Advantageous developments arecorrespondingly described in the appendant claims.

It is proposed in accordance with the invention, if wind powerinstallations are operated on such low-power networks, that their(mechanical and) electrical power is to be controlled in dependence onthe rising network frequency. That is intended to prevent a furtherincrease in the network frequency or to provide for a reduction in thenetwork frequency.

That aspect of the invention is described in greater detail hereinafterby means of an embodiment.

In the drawing:

FIG. 11 shows a frequency/power time graph of a wind power installation,

FIG. 12 shows a side view of a wind power installation,

FIG. 13 shows a block circuit diagram of an inverter of a wind powerinstallation, the inverter being controlled with a microprocessor,

FIG. 14 is a view of a regulating apparatus of a wind powerinstallation,

FIG. 15 is a view illustrating the coupling of a wind power installationto an electrical network, and

FIG. 16 is an alternative view in relation to FIG. 13.

FIG. 11 shows the demand on a wind power installation (of a wind park)to reduce its output power P in dependence on the electrical frequency fof the network. In this case the value of 100% represents the referenceor target frequency (50 Hz, 60 Hz) of the electrical network. The values100.6% and 102% respectively are correspondingly higher values of thenetwork frequency f.

The electrical power of the wind power installation (of the wind park)is not yet reduced for example when there is a rise in the networkfrequency by 0.6% (that is to say to 100.6%). If thereafter the networkfrequency rises still further, then the electrical power of the windpower installation is reduced. In the illustrated example the electricalpower of the wind power installation is reduced to zero power when thereis a rise in the network frequency to 102%.

FIG. 13 shows an embodiment of a wind power installation which satisfiesthat requirement. The wind power installation has adjustable rotorblades (pitch regulation of the rotor blades) so that the mechanicalpower of the wind power installation can be reduced. If for example theangle of incidence of the rotor blades relative to the wind is adjusted,the force on the rotor blades can also be reduced to a desired value.The electrical alternating current from the generator (not shown) whichis connected to the rotor which carries the rotor blades is rectified bymeans of a rectifier 2 and smoothed by means of a capacitor 3. Theinverter 4 then converts the dc voltage into an alternating currentwhich is delivered to the network L₁, L₂, L₃. The frequency of thatoutput current is predetermined by the network. The regulating apparatus5 comprising a microprocessor measures the network frequency andcontrols the power switches of the inverter in such a way that theoutput frequency corresponds to the network voltage (network frequency).If—as described above—the network frequency rises, the electrical poweris reduced, as shown in FIG. 11.

FIG. 14 shows the regulating apparatus according to the invention. Thediagrammatically illustrated rotor 4 of the wind power installation iscoupled to a generator G which provides an electrical power which isdependent on the wind speed and thus the wind power. The ac voltageproduced by the generator G is firstly rectified by means of theinverter and then converted into an ac voltage which is of a frequencycorresponding to the network frequency. The network voltage at thenetwork feed-in point of the network is ascertained by means of thenetwork frequency detector. As soon as the network frequency exceeds apredetermined value—see FIG. 11—, the electrical power output is reducedin order to counteract a further increase in the network frequency.Accordingly, by means of the regulating apparatus, the network frequencyof the network is regulated to a desired network frequency value, or atleast a further rise therein is prevented.

Regulating the feed in that way of the power delivered by the wind powerinstallation makes it possible to avoid or considerably reduce networkfrequency fluctuations.

FIG. 15 shows the coupling of a wind power installation to an electricalnetwork, wherein the electrical power produced by the wind powerinstallation is delivered at the network feed-in point into the network.A plurality of consumers, in the illustrated example diagrammaticallyshown in the form of houses, are connected to the electrical network.

FIG. 16 shows essential components of the control-regulating apparatusin a somewhat different view from FIG. 3. The control and regulatingarrangement has a rectifier, in which the ac voltage produced in thegenerator is rectified. A frequency converter connected to the rectifierconverts the dc voltage which is initially rectified in the intermediatecircuit, into an ac voltage which is fed into the network in the form ofa three-phase ac voltage by way of the lines L₁, L₂, and L₃. Thefrequency converter is controlled by means of the microcomputer which ispart of the overall regulating apparatus. For that purpose themicroprocessor is coupled to the frequency converter. The inputparameters for regulation of the voltage, with which the electricalpower made available by the wind power installation 2 is fed into thenetwork, are the currently prevailing network voltage, the networkfrequency f, the electrical power P of the generator, the reactive powerfactor cos_as well as the power gradient dP/dt. The microprocessorembodies the regulation according to the invention in respect of thevoltage to be fed in, at its desired network frequency.

The present invention further concerns a method of operating a wind parkcomprising at least one wind power installation having an electricalgenerator drivable by a rotor for delivering electrical power to anelectrical network and in particular to the connected consumers thereof.

The present invention also concerns a wind power installation (windpark), in particular for carrying out such a method, comprising a rotorand an electrical generator coupled to the rotor for deliveringelectrical power to an electrical network, and a wind park having atleast two wind power installations.

In the known wind power installations for producing electrical energyfrom wind energy, the generator is operated in parallel mode with anelectrical consumer, frequently an electrical network. During operationof the wind power installation the electrical active power produced bythe generator can vary in dependence on the currently prevailing windspeed. The consequence of this is that the network voltage (magnitudeand/or phase) can also be variable, for example at the feed-in point, independence on the currently prevailing wind speed. The same also appliesfor the current to be fed in.

In a situation involving feeding the electrical power produced into anelectrical network, for example a public power mains howeverfluctuations in the network voltage can occur. However, suchfluctuations are permissible only within very close limits, in theinterests of reliable operation of connected consumers.

Relatively large deviations from the reference value in respect of thenetwork voltage in the power supply network, in particular at themedium-voltage level, can be compensated for example by actuatingswitching devices such as step transformers, insofar as they areactuated when the values exceed or fall below predetermined limitvalues. In that way the network voltage is kept substantially constantwithin predetermined tolerance limits.

The object of the present invention is to provide a method of operatinga wind power installation as well as a wind power installation or windpark, which, even with a fluctuating active power delivery, are in aposition to reduce or at least not significantly increase the unwantedfluctuations in the voltage at a predetermined point in the network incomparison with the situation without a wind power installation orinstallations.

The invention (claims 15 ff) attains that object, in a method of thekind set forth in the opening part of this specification, in that thephase angle φ of the electrical power produced by the wind powerinstallation or installations is varied in dependence on at least onevoltage detected in the network.

In a wind power installation of the kind set forth in the opening partof this specification, that object is attained by an apparatus which iscapable of carrying out the method according to the invention.

In a wind park of the kind set forth in the opening part of thisspecification that object is attained by at least one respectiveapparatus which is suitable for carrying out the method according to theinvention, and a respective voltage detection device, for eachseparately regulatable part of the wind park.

The invention avoids unwanted fluctuations in the voltage applied at theconsumer, in particular the electrical voltage prevailing in a network,by the phase angle of the delivered power being varied in dependence onthe voltage of the consumer or the network. That compensates forunwanted fluctuations in voltage, which arise out of changes in theactive power delivered by the wind power installation or installationsand/or the power taken from the network by the consumers.

In a particularly preferred feature the phase angle is altered in such away that the voltage at at least one predetermined point in the networkremains substantially constant. In that situation to obtain the requiredregulating parameter the voltage at at least one point in the network isdetected.

In particular that point can be a point other than the feed-in point.That detection of the magnitude of the voltage and a suitable change inthe phase angle of the electrical power delivered by the wind powerinstallation or installations can provide a quickly reacting andeffective regulating system.

In a particularly preferred embodiment the values to be set for thephase angle are derived from predetermined characteristic values. Thosecharacteristic values can preferably be provided in the form of a tablein which a previously determined family of characteristic curves isrepresented in the form of discrete values, this making it possible todeduce the phase angle to be set.

In a preferred development of the invention the regulation system candirectly or indirectly provide that, if the voltage fluctuations haveexceeded the predetermined limit values, the voltage is brought backinto the tolerance range again by the actuation of a switching device inthe network, for example a step transformer. At the same time or inrelation thereto the phase angle is set for a predetermined period oftime to a constant value—preferably a mean value, for example zero, inorder once again to be able to compensate for subsequently occurringvoltage fluctuations, by a suitable change in the phase angle.

In a particularly preferred development of the invention suitablevoltage detection procedures and setting operations in respect of thephase angle can also be implemented separately in electrically separateportions of the network, in order to regulate each portion in such a waythat the voltage in each of the portions remains substantially constant.

A further development of the wind power installation according to theinvention advantageously provides a regulating device having amicroprocessor as in that way it is possible to implement digitalregulation.

A preferred development of the wind park set forth in the opening partof this specification provides that there are a respective apparatuswhich is suitable for carrying out the method according to the inventionand a respective voltage detection device for each separatelyregulatable part of the wind park so that electrically separate portionsof the network can also be separately regulated in such a way that thevoltage in each portion of the network remains substantially constant.

The invention is described hereinafter by means of an embodiment of amethod of operating a wind power installation, with reference to thedrawings in which:

FIG. 21 is a simplified view of a wind power installation feeding into anetwork,

FIG. 22 shows a regulating device according to the invention for theoperation of a wind power installation,

FIG. 23 is a view showing the relationship between network voltage andphase angle,

FIG. 24 shows essential components of the regulating device shown inFIG. 22, and

FIG. 25 shows a simplified view of regulation of a plurality of windpower installations, the regulation being separate or common accordingto the respective network situation.

A wind power installation 2 diagrammatically shown in FIG. 21, having arotor 4, is connected to an electrical network 6 which for example canbe a public mains network. A plurality of electrical consumers 8 areconnected to the network. The electrical generator (not shown in FIG.21) of the wind power installation 2 is coupled to an electrical controland regulating apparatus 10 which firstly rectifies the alternatingcurrent produced in the generator and then converts it into analternating current at a frequency which corresponds to the networkfrequency. The control and regulating apparatus 10 has a regulatingdevice according to the invention.

A voltage detection device 22 can be provided at any point 22 in thenetwork 6, the voltage detection device measuring (besides the phase) inparticular the magnitude of the network voltage and returning themeasured value to the regulating device 10 as a suitable regulatingparameter.

FIG. 22 illustrates the regulating device according to the invention.The diagrammatically illustrated rotor 4 is coupled to a generator 12which produces electrical power which can depend on the wind speed. Theac voltage produced in the generator 12 can firstly be rectified andthen converted into an ac voltage of a frequency corresponding to thenetwork frequency.

The network voltage is measured at a location 22 in the network 6 bymeans of a voltage detector (not shown). In dependence on theascertained network voltage—possibly by means of a microprocessor shownin FIG. 4—an optimum phase angle φ is calculated. The network voltage Uis then regulated to the desired value U_(ref) by means of theregulating device.

The electrical power delivered by the generator 12 to the network 6 isregulated by the change in the phase angle.

The view shown in FIG. 23 illustrates the relationship between thevoltage in the network and the phase angle. If the voltage deviates fromits reference value U_(ref) which is between the voltage values U_(min)and U_(max) then, corresponding to the characteristic curve in thegraph, the phase angle φ is altered in such a way that, depending on thesign of the deviation, either inductive or capacitive reactive power isfed into the network in order in that way to stabilise the voltage atthe voltage detection point (at 22 in FIG. 21).

FIG. 24 shows essential components of the control and regulatingapparatus 10 illustrated in FIG. 21. The control and regulatingapparatus 10 has a rectifier 16 in which the alternating currentproduced in the generator is rectified. A frequency converter 18connected to the rectifier 16 converts the initially rectified directcurrent into an alternating current which is fed into the network 6 inthe form of a three-phase alternating current by way of the lines L1, L2and L3.

The frequency converter 18 is controlled by means of a microprocessor 20which is part of the overall regulating device. For that purpose themicroprocessor 20 is coupled to the frequency converter 18. The inputparameters for the microprocessor 20 are the currently prevailingnetwork voltage U, the electrical power P of the generator, thereference value of the network voltage U_(ref) and the power gradientdP/dt. The change according to the invention in the power which is to befed in is implemented in the microprocessor 20.

FIG. 25 shows two wind power installations 2, as an example of a windpark. A regulating apparatus 10 is associated with each of those windpower installations 2 which naturally can also symbolically stand for arespective plurality of wind power installations. The regulatingapparatus 10 detects the voltage at predetermined points 22, 27 in thenetwork 6, 7 and transmits the voltage by way of lines 25, 26 to therespectively associated regulating apparatus 10.

The portions 6, 7 of the network can be connected together or separatedfrom each other, by way of a switching device 23. Provided in parallelwith the switching device 23 is a switching device 24 which makes itpossible for the two regulating apparatuses 10 to be connected togetheror separated from each other, according to the switching condition ofthe switching device 23.

If therefore the two portions 6, 7 of the network are connectedtogether, then the two regulating apparatuses 10 are also connected toeach other so that the entire network is considered as a unit and issupplied by the entire wind park as a unit, wherein the wind park isagain regulated in unitary fashion in dependence on the voltage at thedetection point 22, 27.

If the two portions 6, 7 are separated by the switching device 23, theregulating apparatuses 10 are also separated from each other in such away that a part of the wind park is monitored by a detection point 22 byway of a line 25 by the regulating apparatus 10 and the associated partof the wind park can be correspondingly regulated, while the otherportion of the network 7 is monitored by a detection point 27 by way ofa line 26 by means of the regulating apparatus 10 which correspondinglyregulates the other part of the wind park to stabilise the voltage inthe portion 7 of the network.

It will be appreciated that this division does not have to be limited totwo portions. That division can be taken as far as associating anindividual installation with a portion of the network.

Central regulation of a wind park, in accordance with the invention,essentially aims to provide that the wind park not only feeds electricalenergy into a public power supply network but also at the same time canbe controlled in such a way as to support the network, preferably by theoperator of the public network (power supply utility). Insofar asreference is made to a wind park in the present application, that isalso intended to denote an individual wind power installation and notonly always a plurality of wind power installations, in which respect itis preferably precisely a plurality of wind power installations thatalways forms a wind park.

For the central control of the wind park, in accordance with theinvention, the operator of the public power supply network not only hasa control access by means of a suitable control line (bus system) to thewind park/to the wind power installation, but he also receives from thewind park/wind power installation data, such as for example measuredwind data, data about the status of the wind park, and also for exampledata about the available power (currently prevailing power) (activepower)) of the wind park.

Such a central control can also mean for example that the wind park isentirely taken off the network in certain circumstances, for example ifthe network connection rules which are preset by the operator of thepublic supply network cannot be observed on the part of the wind park.

If for example the voltage in the network falls below a givenpredetermined value, for example to a value of between 70 and 90% of thenetwork voltage, the wind park must be separated from the network withina predetermined time, for example between two and six seconds.

Finally it is necessary to provide that the change in power (dP) of thewind park is not only predetermined by the wind but can also still alterat entire given time intervals. That power parameter is therefore alsoreferred to as the power gradient and specifies by how many percent therespective available power may alter within a predetermined time (forexample per minute). Thus for example it can be provided that the powergradient of the wind park may be at a maximum between 5 and 15%,preferably 10% of the network connection capacity per minute.

Such regulation of the wind park can be effected for example by all windpower installations of a park simultaneously or uniformly increasingtheir power delivery in the predetermined power gradient. It will beappreciated that alternatively it is also possible to envisage that, inthe case of a wind park of for example between 10 and 20 installations,firstly one or two installations (at the respective order of magnitudeof the power gradient) initially feed into the network at full power andthen in accordance with the respective predetermined power gradientfurther installations are cut in, within a predetermined time, until allof the available power of the wind park can be fed into the network.

A further aspect of the wind park regulation according to the inventionis the provision of the reserve power at the level of a percentage, forexample 10%, of the currently available power of the wind park, or afixed value, for example between 500 kW and 1 MW or more per wind park.That reserve power is not to be confused with a park power which exceedsthe network connection power of the wind park. The reserve powerdecisively involves a power reserve (this concerns both active power andalso reactive power) which it does not exceed in the range of thenetwork connection power. That reserve power can be prescribed by theoperator of the public supply network. That is to say, if thereforesufficient wind is available to feed the network connection power fromthe wind park into the network, the power supply utility, by virtue ofthe prescribed control intervention into the wind park, can provide thatthis theoretically possible power is not completely fed into thenetwork, but a part of that power remains available as reserve power. Aparticular aspect of that reserve power is that, in the event of anunexpected failure of power station power (at other locations at whichpower is fed into the network), the network can be stabilised by way ofcalling up the corresponding reserve power.

Accordingly, with the above-indicated central control of the wind park,the power fed into the network is under normal circumstances thereforeless than the power to be made available by the wind park (maximumavailable power), in dependence on the respective power requirement inthe network.

So that this above-described power control procedure can be implementedthe network operator also requires the prescribed data such as windspeed, installation status of the wind park (how many installations arein operation, how many are out of operation or damaged) and preferablyalso the maximum possible active power delivery. In that respect, inregard to the maximum possible active power delivery, the limitation canapply that this has to be provided in the form of data only when itcannot be determined from the wind speed and the installation status.

A normal bus system for example also a standardised bus system, can beused for control of the wind park and also for data supply for the powersupply utility. There are already standardised interfaces for suchstandardised bus systems, for example a Profibus system, so that centralwind park control can also be implemented by means of suitablystandardised control commands.

Supplemental to the foregoing, it can also be provided that the windpark, as from a pre-designed power, that is to say at a total poweroutput of more than 50 MW, is treated as a large-scale power station andthen must also satisfy the conditions for large-scale power stations.

Finally it can also be provided that the wind park is so regulated thatthe network connection value (the network connection capacity) is notexceeded.

Finally when switching on/cutting in the wind park it is also necessaryto provide that unwanted network retroactions do not occur. For example,when switching on/cutting in a wind park, the current may not be higherthan a predetermined value in respect of the nominal current whichcorresponds to the connection capacity. Such a value can be for examplein the range of between 1.0 and 1.4.

If the frequency in the public power supply network rises then—asalready described—it should be provided that, from a given frequencyvalue, for example from 50.25 Hz (with a nominal frequency of 50 Hz),the delivered active power of the wind park is automatically reduceduntil the network frequency is again stabilised at a value as describedabove.

Therefore it must also always be possible to operate the wind park at areduced level of power delivery in order to be able to observe thenetwork requirements. That power regulation also means that the powerdelivery (in particular active power) can be reduced to any desiredvalue in any operating condition and from any operating point.

Thus for example it is possible to implement limitation of the feed-inpower below the available feed-in power if there are dangers in regardto safe reliable system operation, bottlenecks or a risk of overloadingin upstream-disposed networks are to be fixed, there is the danger ofthe formation of an island network, static or dynamic stabilities areendangered, the frequency rise can endanger the entire network system,and for example repair operations or other operational-governedstoppages also have to take place at the power supply utility.

Besides the active power delivery which has already been described aboveand which is to be afforded if necessary, it must also be possible toprovide a given reactive power, in which case it can also be set aswished by the power supply utility, more specifically both in theinductive and also in the capacitive range, that is to say underexcitedand overexcited, in which respect the respective values can bepredetermined for that purpose by the power supply utility.

In that connection, the reference value in respect of reactive powerprovision can be set variably, wherein the reference value presetting iseffected at the network connection nodes for the power factor (cos phi)or a voltage magnitude. It is also possible to predetermine a fixedreference value.

As already described hereinbefore the power delivery is reduced and/orthe wind park is completely taken off the network if frequency values inthe network exceed/fall below certain levels. Thus for example the windpark can be taken off the network when the network falls below a networkfrequency of about 48 Hz (with a 50 Hz network frequency) or at 51 to 52Hz. In that respect, at values below the intended range, it is stillpossible to provide within limits of the range that only a part of thecurrent available power is fed into the network, for example betweenabout 80 and 95% of the current available power.

If for example the network voltage should also fall below apredetermined value, the same also applies here, as in the case of thedeviating network frequency. In other words, when the voltage fallsbelow or exceeds a predetermined network voltage in the given voltage,firstly a reduced power delivery takes place and, when the networkvoltage falls below or exceeds given limit values, the installations arecompletely taken off the network or at least the power fed into thenetwork is set at zero.

Finally it can also be provided that, when given network voltage and/ornetwork frequency values are reached, tried-and-tested shut-down of thewind park is effected, without a power delivery which has already beenreduced being implemented beforehand.

That however also means at the same time that, with given frequencydeviations/voltage deviations within a predetermined range around thenetwork frequency/network voltage, automatic separation of the wind parkfrom the network is not admissible.

Finally, for network protection purposes, it can also be provided thatthe shut-down time when the voltage value is exceeded is markedlyshorter (for example between 50 and 200 milliseconds) than in the caseof voltage reduction protection (shut-down time of more than 1 second,preferably between about 2 and 6 seconds). In that respect, theshut-down time when the value of the upper frequency or lower frequencyexceeds or falls below the predetermined, still just admissible limitvalue is approximately in the region of the shut-down time when thevoltage is in excess (above a predetermined voltage value).

Finally in the event of a fault in the network, for example in ashort-circuit situation, automatic separation of the wind park from thenetwork should not always occur straightaway, but rather the wind parkcan also be controlled in such a way that, depending on the respectivenetwork connection, it still feeds into the network a contribution tothe short-circuit power as apparent power in order in that way still tobe able to afford network support to a certain degree. This means thatthe wind park, at least for a certain time for the duration of a shortcircuit but at a maximum only a few seconds, has to deliver the highestpossible apparent current (apparent power) which however corresponds forexample to once or up to 1.5 times the current which corresponds to thenetwork connection capacity.

The above-described behaviour can also be made dependent on the level ofthe nominal voltage, for example if it exceeds a predetermined value offor example more than 50 kV.

So that the above-described shut-down procedures can take place in goodtime, for example a protective relay (distance protective relay) is tobe installed for the implementation thereof at the network connectionnode.

Finally means should also be provided which, upon start-up of a windpark, synchronise the voltage in the network and that of the wind parkbecause, when the wind park is started up again, asynchronous voltagessensitively disturb the network and can cause it to shut down.

Insofar as in accordance with the present invention the power isregulated below a value of the power which is to be currently madeavailable by a wind park, that can be implemented by various measures.

Thus for example the power can overall be reduced for each individualinstallation so that the entire wind park assumes the desired reducedpower value. As an alternative thereto however it can also be providedthat only individual installations are reduced in respect of their powerfeed-in value so that the total feed-in power value of the wind parkagain assumes the desired value.

Finally it can also be provided that for example a given power madeavailable by the wind park is put into intermediate storage in so-calleddump loads (resistors) or other energy storage means or is convertedinto another form of energy, such that the feed-in value of the windpark assumes the desired value.

The reduction in power output can also be afforded by a procedurewhereby one wind power installation or given wind power installationsare entirely removed from the network so that then once again theoverall power of the wind park (in particular the active power thereof)can be set to the desired value and/or drops below the desired value.

For data transmission of the data in respect of the wind park (winddata, status data, power data etc) or for control of the wind park, itis also possible to provide a wireless communication arrangement so thatthe control data or information data can be wirelessly transmitted andprocessed.

In the case of the above-mentioned wind park regulation, it is also tobe provided that, within the wind park, the procedure also involvesascertaining the value which can be made available as maximum energy andalso then further ascertaining what amount of energy is fed into thenetwork so that, taking the difference amount which is substantially dueto control of the wind park on the part of the power supply utility, itis possible to calculate a feed-in recompense amount which if necessaryis reimbursed.

As already described it is not only possible for the power supplyutility which operates the power supply network to have the possibilityof limiting or restricting the power output of the wind park orindividual wind power installations with the access by way of a controlline, for various reasons (network protection, servo power), but it isalso possible for the operator of the public power supply network, atthe same time, to obtain data relating to the status of the wind park,for example data relating to the maximum available power, wind speed andso forth. As, when the power is restricted to below the currentlyavailable power, the wind park or the wind power installations of a windpark are not put to optimum use, that results in feed-in losses on thepart of the wind power installation operators. Therefore here too theinvention proposes the provision of a virtual current meter whichdetects the difference in respect of that which is not taken off by theintervention on the part of the power supply undertaking into theregulation system and thus the limitation in respect of the wind park orwind power installation power output. Such a ‘virtual current meter’ canon the one hand ascertain from the wind speed the power which is to beavailable and, if at the same time the power supply undertaking oranyone else reduces the power output of individual wind powerinstallations or an entire wind park below the power output which can bemade available, then by an integration operation it is possible toascertain (count) the amount of energy which is not fed into thenetwork. The virtual current meter makes it possible for the operator ofthe wind power installation to obtain remuneration also for the ‘virtualcurrent’, that is to say the current which is not fed into the networkby virtue of the interventions in regulation of the power supply. The‘virtual current meter’ can be installed both at the operator of thewind power installation, in the wind power installations themselveswithin the wind park, at the power supply undertaking or also at themanufacturer of the wind power installations.

Insofar as the present application uses the term wind powerinstallation, that is synonymous with the term wind park. Insofar as thepresent application describes various aspects of the invention they canbe embodied together with the wind power installations or the controlthereof. It is however also possible for the different approachesaccording to the invention to be implemented and claimed singularlywithout the further aspects of the invention, even if the presentapplication usually describes various aspects of the invention together.It will be clear to the man skilled in the art however that variousaspects of the invention can also be implemented and claimed differentlyand the common description thereof is thus not equivalent to them alwayshaving to be implemented and claimed together.

1. A method of operating a wind park comprising a plurality of windpower installations, wherein the wind park is connected to an electricalpower supply network into which the electrical power produced by thewind park is fed and the wind park and/or at least one of the wind powerinstallations of the wind park has a control input, by means of whichthe electrical power of the wind park or one or more individual windpower installation or installations can be set in a range of between 0and 100% of the respective power to be made available, in particular thenominal power, and that there is provided a data processing apparatuswhich is connected to the control input and by means of which thesetting value is set in the range of between 0 and 100%, depending onhow great is the power that the overall wind park provides at its outputfor feeding into the energy network and wherein the operator of theelectrical supply network to which the wind park is connected can adjustthe power delivered by the wind park by way of the control input, thatthe delivered electrical power of the wind park is reduced when thenetwork frequency in the electrical power supply network exceeds orfalls below a given value and the electrical voltage in the electricalpower supply network exceeds and falls below a given value and that thephase angle φ of the phase position between the current which is fed inand the voltage which is fed in is changed in dependence on theelectrical network voltage.
 2. A wind park having a nominal power whichis greater than the power which can/may be fed into the power supplynetwork to which the wind park is connected.
 3. The wind park accordingto claim 2 characterized in that the power of at least one or more windpower installations or all wind power installations of the wind park isthrottled when the maximum possible network feed-in power value isreached.
 4. The wind park according to claim 2 characterized in thatthrottling of the power is of the same magnitude for all wind powerinstallations or is different.
 5. The wind park according to claim 2characterized in that the wind park comprises at least one wind powerinstallation, wherein the power delivered by the wind power installationlimits the amount thereof to a maximum possible network feed-in valuewhich is lower than the maximum possible value of the power to bedelivered (nominal power) and that the maximum possible feed-in value isdetermined by the receiving capacity (power capacity) of the networkinto which the energy is fed and/or by the power capacity of the powertransmission unit or the transformer, by means of which the energyproduced by the wind power installation is fed into the network.
 6. Thewind park according to claim 2 characterized in that the wind powerinstallations which are firstly exposed to the wind within the wind parkare less limited in respect of their power than wind power installationswhich in the wind direction are behind the above-mentioned wind powerinstallations.
 7. A method of operating a wind park comprising at leastone wind power installation having a generator for the delivery ofelectrical power to an electrical network, characterized in that thepower delivered to the network by the wind park is regulated or adjustedin dependence on the network frequency of the electrical network.
 8. Themethod according to claim 7 characterized in that the power which isdelivered by the wind park and fed into the network is reduced when thenetwork frequency of the electrical network exceeds or falls below apredetermined value.
 9. The method according to claim 8 characterized inthat the fed-in power of the wind power installation is reduced when thenetwork frequency is approximately more than 3‰ preferably 6‰ above orbelow the reference value thereof.
 10. A wind park with at least onewind power installation for carrying out the method according to claim7, comprising a rotor and an electrical generator coupled to the rotorfor delivering electrical power to an electrical network, characterizedby a regulating device with a frequency detector for measuring thefrequency of the electrical voltage applied to the network (current) andthat the power delivered to the network by the wind park is adjustablein dependence on the network frequency measured by the frequencydetector or can be adjusted from the exterior.
 11. The wind powerinstallation according to claim 10 characterized in that the regulatingdevice has a microprocessor.
 12. The wind park according to claim 11characterized in that the wind power installation (wind park) has aninverter coupled to the microprocessor.
 13. The wind park according toclaim 7 characterized in that the mechanical power of the wind powerinstallation is produced by the adjustable rotor blades being set intothe wind.
 14. The wind park according to claim 7 characterized in thatthe wind power installation does not deliver any electrical power to thenetwork if the network frequency exceeds or falls below a predeterminedvalue in respect of its reference value, preferably 2% of its referencevalue.
 15. A method of operating a wind park having a wind powerinstallation comprising an electrical generator drivable by a rotor ofthe wind power installation for delivering electrical power to anelectrical network, wherein there is provided a control device whichcontrols the voltage and/or the current of the electrical power to befed into the network, characterized in that there are provided means formeasuring the voltage at least at one location in the electrical networkand that the measured value is fed to the control device and the controldevice implements a phase angle change in dependence on the measuredvalue, wherein the phase angle φ determines the phase position betweenthe current which is fed in and the voltage which is fed in.
 16. Themethod according to claim 15 characterized in that the phase angle φ ischanged in such a way that the voltage at least one predetermined pointin the network remains substantially unchanged.
 17. The method accordingto claim 15 characterized in that the voltage is detected at least onepredetermined point in the network.
 18. The method according to claim 15characterized in that the voltage is detected at a different point fromthe feed-in point.
 19. The method according to claim 15 characterized inthat the values which are to be set for the phase angle φ are derivedfrom predetermined characteristic values.
 20. The method according toclaim 15 characterized in that the regulation can directly or indirectlyimplement actuation of a switching device in the network.
 21. The methodaccording to claim 15 characterized in that for portions of the networkcorresponding voltage detection procedures and regulating procedures bymeans of the phase angle φ are effected separately.
 22. A wind powerinstallation characterized by an apparatus for carrying out the methodaccording to claim
 15. 23. A wind park having at least two wind powerinstallations characterized by an apparatus for carrying out the methodaccording to claim 15 and a respective voltage detection device for eachseparately regulatable part of the wind park.
 24. A wind park inparticular according to claim 22 characterized in that, for thesituation where the voltage in the power supply network falls to a valuebelow the nominal voltage, for example to a value of between 70 and 90%of the network voltage value, the wind park is separated from thenetwork within the predetermined very short period of time, for examplebetween 2 and 6 seconds.
 25. The wind park according to claim 24characterized in that the increase or reduction in the power of the windpark is limited to a value of between about 5 and 15%, preferably 10%,of the network connection capacity of the wind park per minute.